1. Field of the Invention
The present invention relates generally to “manway” covers for access to enclosed spaces such as tanks, conduits, storage areas, heat exchanger tubes. Particularly, the present invention relates to mechanisms to assist in the removal of “manway” covers. More particularly, the present invention relates to mechanisms for handling the removal and installation of “manway” covers that are too heavy to be handled by an unaided individual.
2. Description of the Prior Art
Manway covers are typically large, heavy, metal plates that are bolted to an opening. For purposes of the present invention, the definition of “manway covers” expressly means any heavy covers or closures having a weight of thirty-five (35) pounds or more used on pressure vessels, vacuum vessels, atmospheric vessels, heat exchangers, heat exchanger channel covers, heat exchanger channels, heat exchanger bonnets, or any type of blanking plate and is not construed to be limited to only covers used on openings that are dimensionally-sized to allow passage of a man. The most common are circularly-shaped and mate to a flange by way of a plurality of bolts evenly spaced around the periphery of the opening. However, it should be understood that the heavy covers may be any shape. The defined manway covers typically provide access to enclosed spaces such as tanks, conduits, storage areas, transfer tubes, pressure vessels, vacuum vessels, atmospheric vessels, heat exchangers, heat exchanger channel covers, heat exchanger channels, heat exchanger bonnets, and the like.
Routine servicing and inspection requirements as well as other operating conditions necessitate periodic removal of these manway covers. In view of the typical location and weight of the manway covers, it is not a simple task to remove the cover or to re-install the same. Removal is currently accomplished with the use of hand operated davit swing arms, chain falls, ratchet hoists, portable hinge devices, and brute force. Except for davit swing arms and portable hinge devices, it is necessary during the removal process to lower the covers a distance to a level surface.